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Hypothermia System

Without reference, identify principles about Hypothermia Systems with at least 70 percent accuracy. Hypothermia System. Hypo/Hyperthermia Unit Primary Uses Maintain normal temperature in patients during and after surgery Decrease and stabilize the body temperature of febrile patients

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Hypothermia System

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  1. Without reference, identify principles about Hypothermia Systems with at least 70 percent accuracy.

  2. Hypothermia System • Hypo/Hyperthermia Unit Primary Uses • Maintain normal temperature in patients during and after surgery • Decrease and stabilize the body temperature of febrile patients • Elevate the body temperature of victims of accidental hypothermia

  3. Hypothermia System • Mechanisms of Heat Loss • A healthy person resting at room temperature generates metabolic heat at a rate of approximately 70kcal/hr for a 154lb individual. Without heat loss from the environment, metabolic heat would cause body temperature to rise about 1 C/hr • Body heat loss occurs by several mechanisms • Conductive heat loss • Heat loss to cooler objects in contact with the skin • Usually negligible (2%), even when a patient is recumbent (lying down) • Contacted surfaces are rapidly warmed to near body temperature • Most surfaces on which patients lie are poor thermal conductors

  4. Hypothermia System • Convective heat loss • Increases rapidly with wind velocity • Accounts for less than 20% of total heat loss at room temperature • When air temperature exceeds body temperature, the body gains heat energy • Radiational heat loss • Heat loss from transition of infrared radiation to cooler objects in the environment • Accounts for about 65% of the total heat loss at room temperature for an unclothed patient • Heat loss can be significantly reduced by covering exposed portions

  5. Hypothermia System • Temperature drops during surgery • Ideally, the minimum core temperature during surgery should be 35 C • This may be too great a drop for very old, very young, or cardiac patients • Many researchers report much larger temperature drops-even down to 30 C-during surgery • Average Drops • 0.3° C/hr for 20 year old patients • 1.1° C/hr for 80 year old patients

  6. Hypothermia System • Temperature drops of 3-4 C, caused by the following mechanisms, are common during surgical procedures: • Convective heat loss occurs because • Large amounts of the body's surface are exposed in the OR • Where humidity is low and temperatures are typically 18-19 C • Hypothermia is common during pediatric surgery • The infant's relatively large body surface area, which increases heat loss to the atmosphere 2 Relatively small body mass for conserving heat

  7. Hypothermia System • Increased evaporative heat loss occurs: • When the patient breathes in dry anesthetic gasses • Volatile cleaning solutions are applied to the skin • Moist surgical wounds are exposed to the air • Infusing cold or room-temperature fluids (e.g. blood) contributes to heat loss • Anesthetic agents • Can affect the patient's thermoregulatory system promoting heat loss • Halothane causes blood vessels to enlarge reducing sensitivity to catecholamines, which promote heat gain

  8. Hypothermia System • Large temperature drops during surgery pose significant dangers • The risk of ventricular fibrillation increases and is especially great for cardiac patients • Patients who are already hypothermic are more susceptible to fibrillation caused by infusing cool fluids • Heat loss in the OR must be regained with increased circulatory and ventilatory effort in the postoperative period, when these functions in the patient may be compromised • Even a small temperature change will cause a large increase in a patient's oxygen uptake • Which is hazardous for cardiac patients • Shivering during this period may increase 02 uptake and CO2 production fivefold

  9. Hypothermia System • Methods of inducing temperature changes • Invasive methods of raising body temperature • Most rapid • Usually reserved for severe hypothermia • These methods are not preferred • Require compromising the closed system of the body • Possibly enhancing the chance of infection or shock • Other methods of raising the body temperature may be slow. (hypothermia machines)

  10. Hypothermia System • External rewarming method • The core temperature may continue to drop • Factors reducing the long-term effectiveness of external rewarming in raising core temperature: • Vasodilatation • Inhibition of metabolism • Shivering

  11. Hypothermia System • Lowering body temperature • Clinicians may deliberately lower the temperatures of surgical, as well as febrile patients by: • Infusing cold water or using ice baths • Ice packs • Cold air ventilation • Sponge baths • Hypothermia machines

  12. Hypothermia System • Reducing body temperature slows metabolism by reducing the speed of biochemical reactions • When intentionally induced during cardiac surgery, or neurosurgery: • Hypothermia reduces the body's need for • Blood flow • Oxygen • Waste elimination • Thereby permitting greater tolerance of surgical procedures and reducing tissue injury

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